The Utah Dept. of Transportation used a related method to replace a number of bridges along I-80 this summer.
Instead of building each new bridge on site, they used a large staging area adjacent to the freeway to build each bridge out of the flow of traffic, thus not affecting traffic on the freeway or cross streets.
Then over the course of a few weekends, they closed the freeway and used a large lift/roller to move all of the bridges in place and set them over the roadway.
http://www.udot.utah.gov/innovate80/
I'm no engineer, but it sounds like it was pretty succesful and saved a lot of time, money and lessened traffic impacts compared to traditional methods.
One of the new bridges being moved into place:
